Well, there are dependancies that have to be looked at as far as tuning goes, and that can be figured into a solution if given the right parameters. Not only does it rely on recommended characteristics, but a preference as well. If you are given a driver that works most efficient at say, 37Hz tuning for proper compression, but you want to go lower.....go lower and you can benefit from that jsut as much if you keep the design simple in form (conventional) and not too complex, as the response curve and phase will not change much from those differences in tuning. But if it calls for say 46Hz tuning, you may want to find a proper way to control its output more in the lower end, which again, can be done with a bit of figuring.
At the end, it really depends on those two factors, 1. your preference, 2. proper compression. The first one does not need calculation lol. The second one can be either extensive in figures or very simple depending on the design goal and physics. :D Hope that helps.